1. Field of the Invention
The present invention relates to an electron source forming substrate used in forming an electron source and to the electron source and an image forming apparatus using the substrate.
2. Related Background Art
Heretofore in the past, there have been known electron-emitting devices, which are broadly classified into two types using thermionic electron-emitting devices and cold cathode electron-emitting devices. For the cold cathode electron-emitting devices, there are available field emission type (hereinafter referred to as xe2x80x9cFE typexe2x80x9d),metal/insulating layer/metal type (hereinafter referred to as xe2x80x9cMIM typexe2x80x9d), surface conduction type electron-emitting device and the like.
As an example of the FE type, there are known those devices as disclosed in W. P. Dyke and W. W. Dolan, xe2x80x9cField emissionxe2x80x9d, Advance in Electron Physics, 8.89 (1956) or C. A. Spindt. xe2x80x9cPhysical properties of Thin-Film Field Emission Cathodes with Molybdenium Conesxe2x80x9d, J. Appl. Phys., 47,5248 (1976) and the like.
As an example of the surface conduction type electron-emitting device type, there are known those as disclosed in M. I. Elinson, Recio Eng. Electron Phys., 10,1290 (1965) and the like.
The surface conduction type electron-emitting device utilizes a phenomenon where electron emission occurs by letting current flow in parallel with a film surface on a thin film of a small area formed on a substrate. For the surface conduction type electron-emitting device, there are reported those which use SnO2 thin film by the above described Elinson and the like, Au thin film xe2x80x9cG. Dittmer: xe2x80x9cThin solid Filmsxe2x80x9d, 9, 317 (1972)xe2x80x9d, In2O3/SnO2 thin film xe2x80x9cM. Hartwell and C. G. Fonstad: xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d 519 (1975)xe2x80x9d, carbon thin film xe2x80x9cHisashi Araki et. al: SHINNKUU Vol.26, No. 1, 22 pages (1983)xe2x80x9d and the like.
To utilize the above described electron-emitting device by holding an electron source arranged and constructed on a substrate inside an envelope which is kept vacuum inside, it is necessary to connect the electron source to the envelope and other members. This connection is usually performed by heating and fusion by using frit glass. The heating temperature at this time is typically approximately 400xc2x0 C. to 500xc2x0 C. and the time thereof is typically approximately ten minutes to one hour, which differs depending on the size of the envelope.
For the material of the envelope, in view of simplicity and reliability of the connection by frit glass and relatively inexpensive cost, soda lime glass is preferably used. Also, because a high strain point glass where a strain point is raised by replacing a part of Na by K is easy for frit connection, it can be preferably used as well. Also, with regard to the material of the substrate of the above described electron source, in view of reliability of the connection to the envelope, similarly the soda lime glass or the above described high strain point glass is preferably used.
The above described soda lime glass contains alkali element metal as its component and particularly contains the large volume of Na as Na2O. Na element is easy to diffuse by heat and, therefore, when exposed to high temperatures during a processing, Na is sometimes diffused into each type of members formed on the soda lime glass, particularly into the member constituting the electron-emitting device, thereby deteriorating its characteristics.
It was reveled that the above described influence by Na sometimes occurs, but to a lessened degree, by that much if Na content is small when the above described high strain point glass is used as the substrate of the electron source.
As means for reducing the above described influence of Na, for example, there are disclosed in Japanese Patent Application Laid-Open No. 10-241550, EP-A-850892 an electron source forming substrate where the concentration of Na of the surface area of the side where the electron-emitting device of the substrate containing Na is at least arranged is smaller than that of other area and also an electron source forming substrate having a phosphorus containing layer.
It is an object of the present invention to provide at a low cost an electron source forming substrate where time changes in the electron-emitting characteristics of the electron-emitting device is reduced, and to provide the electron source as well as an image display apparatus using the substrate.
The present invention provides the electron source forming substrate where the electron emitting device are arranged, comprising a substrate and an insulating material film which is disposed on the surface of the substrate, at which surface the above described electron-emitting device of the above described substrate is arranged, and contains a plurality of metallic oxide particles having an average particle size within the range of 6 nm to 60 nm as expressed in a median value.
Also, the present invention provides the electron source forming substrate where the electron emitting device are arranged, comprising a substrate and an SiO2 film which is disposed on the surface where the above described electron-emitting device of the above described substrate is arranged, and which contains a plurality of metallic oxide particles having an average particle size within the range of 6 nm to 60 nm as expressed in the median value.
Also, the present invention provides the electron source, comprising the substrate and the electron-emitting device arranged on the above described substrate, wherein the above described substrate is any of the above described electron source forming substrates.
Also, the present invention provides the image display apparatus comprising an envelope and an image display member for displaying images by irradiation of the electron from an electron-emitting device and the above described electron-emitting device, wherein the substrate where the above described electron-emitting devices are arranged is any of the above described electron source forming substrates.
The electron source forming substrate of the present invention is an electron source forming substrate wherein the electron-emitting device is arranged, comprising the substrate and the insulating material film which is disposed on the surface where the above described electron-emitting device of the above described substrate is arranged, and which contains a plurality of metallic oxide particles having an average particle size within the range of 6 nm to 60 nm as expressed in the median value.
In the above described electron source forming substrate of the present invention, as still further preferable embodiments,
the above described insulating material film further contains phosphorus,
the above described insulating material film further contains phosphorus having 1 weight portion to 10 weight portions,
the thickness of the above described insulating material film is within the range of 200 nm to 600 nm,
the thickness of the above described insulating material film is within the range of 300 nm to 400 nm, on the above described insulating material film, a film comprising the insulating material is laminated,
the thickness of the film comprising the above described insulating material is within the range of 20 nm to 150 nm, and
the thickness of the film comprising the above described insulating material is within the range of 40 nm to 100 nm.
Also, the electron source forming substrate of the present invention is an electron source forming substrate where the electron-emitting device is arranged, comprising the substrate and the SiO2 film which is disposed on the surface where the above described electron-emitting device of the above described substrate is arranged, and contains a plurality of metallic oxide particles having an average particle size within the range of 6 nm to 60 nm as expressed in the medial value.
In the above described electron source forming substrate, as still further preferable embodiment:
the above described SiO2 further contains phosphorus,
the above described SiO2 further contains phosphorus having one weight portion to 10 weight portions,
the thickness of the above described SiO2 film is within the range of 200 nm to 600 nm,
the thickness of the above described SiO2 film is within the range of 300 nm to 400 nm,
on the above described SiO2 film, a film comprising SiO2 is further laminated,
the thickness of the film comprising the above described SiO2 is within the range of 20 nm to 150 nm, and
the thickness of the film comprising the above described SiO2 is within the range of 40 nm to 100 nm.
In the above described electron source forming substrate of the present invention, as still further preferable embodiments,
the average particle size as expressed in the above described median value is within the range of 15 nm to 30 nm,
the above described metallic oxide particles are electronically conductive oxide particles,
the above described metallic oxide particles are the particles of the metal chosen from Fe, Ni, Cu, Pd, Ir, In, Sn, Sb and Re,
the above described metallic oxide particles are the particles of SiO2, and
the above described substrate is a substrate containing sodium.
Also, the electron source of the present invention is an electron source comprising the substrate and the electron-emitting device disposed on the above described substrate, wherein the above described substrate is the above described electron source forming substrate of the present invention.
In the above described electron source of the present invention, as still further preferable embodiments,
the above described electron-emitting device is an electron-emitting device comprising an conductive film containing an electron-emitting portion,
a plurality of the above described electron-emitting devices are matrix-wired in a plurality of row-directional wirings and in a plurality of column-directional wirings,
the above described electron-emitting device is an electron-emitting device comprising an conductive film containing an electron-emitting portion between a pair of electrodes, and
a plurality of the above described electron-emitting devices are matrix-wired by a plurality of row-directional wirings and a plurality of column-directional wirings and the above described one pair of electrodes are constituted by the material comprising platinum as the principal component and the above described wirings are constituted by the material comprising silver as the principal component.
Also, the image display apparatus of the present invention is an image display apparatus comprising the enveloper and the image display member which is arranged inside the above described enveloper and displays images by irradiation of the electron from the electron-emitting device and the above described electron-emitting device, wherein the substrate where the above described electron-emitting device is arranged is the above described electron source forming substrate of the present invention.
In the above described image display apparatus of the present invention, as still further preferable embodiments,
the above described electron-emitting device is an electron-emitting device comprising the conductive film containing the electron-emitting portion,
a plurality of the above described electron-emitting devices are matrix-wired by a plurality of row-directional wirings and a plurality of column-directional wirings,
the above described electron-emitting device is an electron-emitting device comprising the conductive film containing the electro-emitting portion between a pair of electrodes, and
a plurality of the above described electron-emitting devices are matrix-wired by a plurality of row-directional wirings and a plurality of column-directional wirings and the above described one pair of electrodes are constituted by the material comprising platinum as the principal component and the above described wirings are constituted by the material comprising silver as the principal component.
According to the study by the present inventors, it was revealed that, depending on the insulating material film containing metallic oxide particles formed as an Na block layer on the substrate, the type and the shape of the film containing, for example, SiO2 formed on this insulating material film, dope materials and the film thickness, characteristics change largely and only when an optimum configuration is given, the effect thereof is sufficiently demonstrated.
It was also revealed that not only by the configuration of the film, but also by the electrode, the wiring, the material of the electron-emitting device film and the like formed on the substrate, a process and a heat history, the optimum configuration can change.
In the electron source forming substrate of the present invention, by having the insulating material film containing a plurality of metallic oxide particles having an average size of particle within the range of 6 nm to 60 nm as expressed in the median value on the surface where the electron-emitting device of the substrate is arranged, specifically, the SiO2 film containing SnO2 particles, Na in a glass substrate containing mainly SiO2 of 50 to 75 weight % and Na of 2 to 17 weight % can be effectively blocked. For this reason, the electron-emitting device using the electron source forming substrate of the present invention can reduce elapsed time changes of the electron-emitting characteristics and obtain the steady electron-emitting characteristics.
Also, particularly by using the electronically conductive oxide particles as the above described metallic oxide particles, much steadier electron-emitting characteristics can be obtained. In the present invention, the term electronically conductive oxide particle is used for ion conductivity and the disposing of the electronically conductive material has the following advantages.
That is, by disposing a layer containing the electronically conductive material on the substrate, the substrate surface shows electrical conductivity and unsteadiness during the drive by charge-up can be controlled. To provide this electrical conductivity, when the iron electrically conductive material is used, a voltage relative to the drive is applied and ion moves while the voltage is applied for a long time and as a result the ion is segregated, thereby bringing about a situation where electron source characteristics become unsteady. This is considered to occur because the time required for the movement of the ion is, for example, so much that the movement of the iron is not fully restored between pulses, that is, within a quiescent period in the case where the voltage relative to the drive is applied in the pulse form. Such a segregation of the ion has a bad influence on the electron source characteristics. Accordingly, particularly when the substrate has a layer containing the electronically conductive material and the conduction is mainly due to the electron conduction, the segregation of the ion hardly occurs so that the influence on the above described electron source characteristics can be avoided.
Also, for the above described metallic oxide particles, it is particularly preferable to use the particles of SnO2. This SnO2 is in the market at relatively low cost and the conduction is mainly due to the electron conduction and can be easily used as solution for coating and film depositing.
Also, by doping phosphorus into the insulating material film (for example, SiO2 film), the resistance value of the film can be easily controlled. Also, it was revealed that an adequate doping of phosphorus enhances the block effect of sodium. Although this mechanism is not yet clarified, it is considered that sodium in the substrate glass forms some compounds with phosphorus and is fixed there so that the diffusion of sodium into the substrate surface is restrained.
Also, on the above described insulating material film (for example, SiO2 film) which is a first layer, a film (for example, SiO2 film) comprising the above described insulating material which is a second layer is further formed so that sodium block effect can be much more improved than the block effect expected from each film alone.
Also, it was revealed that when, for example, a burning process of an approximately 500xc2x0 C. is repeated by using platinum for the electrode of the electron-emitting device and silver for wiring and, the diffusion of sodium into the surface is large. Even in such a case, by using the sodium block layer of the present invention, the diffusion of Na can be effectively blocked.